Multi-element dental implant

ABSTRACT

Suprastructure for a dental implant is provided with a false stump defining a prosthesis base plate, a shank for anchoring the false stump, with the shank including partially extending slots forming surface segments capable of radial expansion, a hollow core opening at a free end of the false stump and including a converging ramp at the free end, a series of balls positioned in the hollow core, with one of the balls abutting against the converging ramp so as to be retained thereby and to exert a spacing pressure onto the surface segments, and a screw abutting against a first ball of the series of balls to cause the balls to be moved against the converging ramp. The suprastructure can be used in combination with a tubular implantal stump adapted to be anchored in the osseous site and to accommodate the shank of the suprastructure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a multi-element dental implant for furthergrafting and anchoring of a dental prosthesis onto an osseous site. Theinvention includes the component parts of this implant as well asimplant dentures made therefrom.

2. Discussion of Background Information

Dental implantology shows an increasing tendency leading to the use ofmulti-element implants that are composed of two separate elements, withthe grafting thereof being successively effected. These multi-elementimplants are provided with an implantal stump composed of a tubularelement which is anchored in the osseous site, and a suprastructurecomposed of an anchoring shank formed on the implantal stump and of afalse stump that serves as a prosthesis base plate. Further, in implantssuch as the so-called normal implants, the false stump and the anchoringshank have collinear axes; whereas, in implants such as the so-calledpreangulated implants, the axes form an angle up to 20°.

First, the implant stump is anchored by screwing or any other way (DE1,961,531, EP 0,114,955, or U.S. Pat. No. 3,708,883) in the osseoussite, then the suprastructure is attached to the implantal stump bymeans of the anchoring shank so as to cause the false stump to take asuitable position. Actually, such anchoring in the implantal stump ofthe shank is achieved by two methods.

In one method the suprastructure shank is composed of a smooth bar, andis permanently sealed within the tubular implantal stump by using acement. However, in this method, should clinical problems arise, then noremoval of the suprastructure will not be possible.

In the other known anchoring method, the suprastructure shank is screwedinto the implantal stump through conjugate threading and tapping asprovided on these elements (See U.S. Pat. No. 3,589,011). In this methodthe suprastructure is releasable. However, positioning is inaccurate andhazardous, so much in the longitudinal direction (along the implantaxis), because a determination, upon screwing, of the tightening stoplimit proves difficult and relates to the orientation of thesuprastructure about its axis, which is conditioned upon the finalthread position. This angular inaccuracy forms a serious defectimpairing preangulated implants, so that suitable positioning can hardlybe made using this anchoring method.

SUMMARY OF THE INVENTION

The present invention intends to provide an improved multi-elementimplant, exempt from the above-mentioned defects. The invention aims atachieving accurate anchoring in the implantal stump (deep along thelongitudinal axis and angularly about such axis) of the suprastructurewhile maintaining easy removal, if necessary.

Accordingly, the multi-element dental implant involved in the inventionis of the type comprising a suprastructure provided with a false stumpused as a prosthesis base plate and a shank for anchoring thereof, and atubular implantal stump adapted to be anchored in the osseous site andto accommodate the suprastructure shank. In accordance with the presentinvention, the implant is characterized in that:

The suprastructure comprises a hollow core extending lengthwise therein,the hollow core opening at the free end of the false stump and beingprovided at the free end of the shank with a converging ramp,

the suprastructure shank comprises a number of slots extending partiallylengthwise therein from its free end so as to define several surfaceareas able to withstand radial expansion,

several balls are accommodated within the suprastructure hollow core asa series maintaining the balls in mutual contact, the latter thereofabutting against a cone-shaped ramp of the shank so as to be retainedthereby, and to exert onto surface areas of the shank a spacingpressure,

a screw is screwed within a tapped portion of the hollow core in thevicinity of the free end of the false stump, the screw abutting againstthe first ball so as to cause the series of balls to be moved and fixed.

Hence, in the implant of the invention, the tubular implantal stumpwhich is of a type known per se, is anchored in the osseous siteconventionally, such as by screwing or any other way already known. Thesuprastructure is anchored in this implantal stump by inserting itsanchoring shank therein and positioning it suitably, angularly and alongthe longitudinal axis. Then, a mere actuation of the upper screw willsuffice to entail both the shank expansion and setting thereof insidethe implantal stump. Such an operation does not modify thesuprastructure angular axial position which results in thesuprastructure being accurately set into a selected position. Removal ofthe suprastructure is achieved by simply actuating the screwcounterclockwise, whereby the anchoring shank is released in the radialdirection, and can be extracted.

The implant in accordance with the invention can be of the normal type,such as the shank and false stump of the suprastructure having collinearaxes. Also, the implant can be preangulated so that the axes of theshank and false stump form a predetermined angle, e.g., 6°, 12° or 20°.

The invention also relates to a suprastructure as above defined fordental implant, characterized in that it comprises a hollow anchoringshank provided with a number of longitudinal slots defining severalsurface areas able to withstand radial expansion and the suprastructureis provided with a hollow core which is bored longitudinally therein,and comprises, at the end of the shank, a converging ramp, and, at theend of the false stump, a tapped portion. A series of balls ispositioned within the hollow core between the converging ramp and ascrew that is screwed into the tapped portion.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features, objects and advantages of the invention will be apparentfrom the description as follows refering to the appended drawings, whichrepresent two examplary embodiments, that form part of the presentdescription:

FIGS. 1 and 2 are axial cross-sections at expanded scale showing apreangulated implant in accordance with the invention, suprastructureand implantal stump thereof, respectively,

FIG. 3 is a transversal cross-section of the suprastructure through aplane AA,

FIG. 4 is a schematic cross-section showing both the implant andprosthesis thereof as positioned on the site,

FIG. 5 is a schematic cross-section of another embodiment (normalimplant) ready to accommodate a clipped prosthesis.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The multi-element dental implant shown for example at FIGS. 1-4 (scaleapproximatively 8) is a preangulated implant whereof the angle is equalto 12°. It is composed of an implantal stump 1 (FIG. 2) made for exampleof titanium, which takes a tubular form inclusive of a cylindricalhollow core 1a that is closed by a hemispherical bottom plate 1b. On itsouter cylindrical face, this element is provided with a threading 2 topermit conventional anchoring thereof in the maxillary site.

Further, the other implant element, the so-called suprastructure 3 (FIG.1), is also made of titanium and comprises a false stump 4, shank 5 anda gingival junction 6 formed therebetween. The false stump longitudinalaxis X forms together with the shank longitudinal axis Y a 12° angle.Moreover, shoulders such as 6a and 6b define the gingival junction 6.These are expected to correspond with the bone/gum interface and the gumouter surface, respectively, as shown in FIG. 4.

In the suprastructure 3 is bored in either part lengthwise longitudinalaxis X, Y thereof a hollow core 7 with circular cross-section. At thefree end of the shank 5, this hollow core 7 comprises a truncated ramp 8having an apex angle thereof which is in particular, within 45° and75°more preferably about 60°. Additionally, the hollow core 7 is tappedto part of the length 9 thereof at the free end of its false stump.

The suprastructure shank 5 shows an outer diameter which is slightlyinferior to the bore of the implantal stump 2 so as to get accommodatedtherein with smooth Friction. The suprastructure is divided partiallylengthwise into several segments such as 5a by a number of longitudinalslots 13 (herein in the number of four) starting from the shank freeend. Thus, the this shank can withstand a radial expansion in view ofthe resilient free motion of the segment 5a.

The hollow core 7 of the suprastructure is herein provided with severalballs such as 11a, 11b formed in a series in mutual contact between thecone shaped ramp 8 and a screw 10 screwed in the tapped portion 9. Theseballs are given a diameter slightly smaller than that of the hollow core7 so as to be able to move therein in the longitudinal direction.Moreover, the last ball 11a, the so-called expansion ball, comes intocontact with the cone shaped ramp 8, whereas the other balls such as 11btransfer the longitudinal motion of the screw 10 thereto, the first ballof the series having contact therewith.

The screw 10 comprises a recess 10a whereby handling thereof can be madewith a sharped-nosed key. Hence, the practitioner can generate alongitudinal displacement of the ball series that causes the expansionball 11a to engage in the cone shaped ramp 8, and, consequently, causespacing pressure to be applied onto the segments 5a. Further, thepractitioner can release the same segments by performing a reversal ofthe operative steps.

FIG. 4 shows the implant as grafted to site with prosthesis 12 thereof.The practitioner anchors the implantal stump 1 within the osseous siteof the maxillary conventionally. Thereafter, he introduces thesuprastructure shank 5 in the implantal stump. Further, he axially andangularly positions the shank to bring the false stump 4 into idealposition and orientation and then he so acts on the screw 10 as toposition the shank 5 in its expanded condition and set it in theimplantal stump. The suprastructure can be removed, as needed, byoperating the screw through a reverse operating sequence to release theshank segments.

Moreover, the prosthesis 12 is secured to the false stump 4 by any knownmeans. In the example shown, this prosthesis is made of ceramics andcomprises an internal metal cover 12a which is bonded to the falsestump. Of course, the false stump of the implant can, in accordance withthe invention, be adapted to provide use of any other type ofprosthesis, anchoring, e.g., anchoring by means of screwing (on behalfof conjugated threading and tapping as formed onto the false stump andthe prosthesis or by clipping as shown by FIG. 5).

This FIG. 5 applies to the case of a normal implant (common axis Zshared by the shank and the false stump), whereof the false stump isequipped with the clipping head.

It should be noted that the anchored prosthesis may, upon thecircumstances be provided with a channel having dimensions larger thanthe recess 10a of the screw to access thereat and act thereon upon theprosthesis anchoring. The prosthesis so anchored is of the fixed typealthough the practitioner can readily remove it at any time. The channelproviding access to the screw 10 can be closed by any means to beextracted by the practitioner when required.

I claim:
 1. A suprastructure for a dental implant, comprising:a falsestump defining a prosthesis base plate and a shank; said shankcomprising a plurality of longitudinal slots defining a plurality ofsurface segments capable of radial expansion; a hollow corelongitudinally extending in said false stump and said shank, andcomprising a converging ramp at an end of said shank and a tappedportion at an end of said false stump; a series of balls positionedwithin said hollow core between said converging ramp and a screw, saidscrew positioned within said tapped portion.
 2. The suprastructureaccording to claim 1, comprising a prosthesis attached to said falsestump.
 3. The suprastructure according to claim 2, wherein saidprosthesis is attached to said false stump by bonding screwing orclipping.
 4. The suprastructure according to claim 1, wherein said screwcomprises a recess.
 5. A suprastructure, comprising:a false stumpdefining a prosthesis base plate; a shank for anchoring said falsestump, said shank comprising a plurality of slots partially extendinglengthwise from a free end of said shank defining a plurality of surfacesegments capable of radial expansion; a longitudinally extending hollowcore in said suprastructure opening at a free end of said false stumpand comprising a converging ramp at said free end of said shank; aseries of balls in mutual contact positioned in said hollow core, one ofsaid series of balls abutting against said converging ramp so as to beretained thereby and to exert a spacing pressure onto said plurality ofsurface segments; and an element positioned in said hollow core in avicinity of said free end of said false stump abutting against a firstball of said series of balls to cause said series of balls to be movedinto position with said one ball against said converging ramp.
 6. Thesuprastructure according to claim 5, wherein said element comprises ascrew positioned within a tapped portion of said hollow core.
 7. Thesuprastructure according to claim 6, wherein said screw comprises arecess.
 8. The suprastructure according to claim 6, wherein saidconverging ramp comprises a truncated ramp having an apex angle ofbetween 45° and 75°.
 9. The suprastructure according to claim 8, whereinsaid converging ramp comprises a truncated ramp having an apex angle ofabout 60°.
 10. Multi-element dental implant for further grafting andanchoring of a prosthesis onto an osseous site, comprising:(a) asuprastructure comprising:(i) a false stump defining a prosthesis baseplate, (ii) a shank for anchoring said false stump, said shankcomprising a plurality of slots partially extending lengthwise from afree end of said shank defining a plurality of surface segments capableof radial expansion, (iii) a longitudinally extending hollow core insaid suprastructure opening at a free end of said false stump andcomprising a converging ramp at said free end of said shank, (iv) aplurality of balls serially positioned in said hollow core, each of saidplurality of balls being in contact with another of said plurality ofballs, one of said plurality of balls abutting against said convergingramp so as to be retained thereby and to exert a spacing pressure ontosaid plurality of surface segments, and (v) a screw positioned within atapped portion of said hollow core in a vicinity of said free end ofsaid false stump, said screw abutting against a first ball of the seriesof said plurality of balls to cause said series of balls to be movedinto position; and (b) a tubular implantal stump adapted to be anchoredin the osseous site and to accommodate said shank.
 11. The dentalimplant according to claim 10, wherein said converging ramp comprises atruncated ramp having an apex angle of between 45° and 75°.
 12. Thedental implant according to claim 11, wherein said shank and said falsesump have collinear axes.
 13. The dental implant according to claim 11,wherein said shank and said false stump have axes defining apredetermined angle therebetween.
 14. The dental implant according toclaim 11, wherein said screw includes a recess.
 15. The dental implantaccording to claim 10, wherein said converging ramp comprises atruncated ramp having an apex angle of about 60°.
 16. The dental implantaccording to claim 15, wherein said shank and said false stump havecollinear axes.
 17. The dental implant according to claim 15, whereinsaid shank and said false stump have axes defining a predetermined angletherebetween.
 18. The dental implant according to claim 10, wherein saidshank and said false stump have collinear axes.
 19. The dental implantaccording to claim 10, wherein said shank and said false stump have axesdefining a predetermined angle therebetween.
 20. The dental implantaccording to claim 10, wherein said screw includes a recess.